Morphogenesis of multicellular organisms requires the synthesis and assembly of complex extracellular structures. Although several extracellular proteins have been identified, little is known about how these proteins actually function to produce organized macromolecular structures. The long-term goals of this proposal are to understand how extracellular proteins assemble into macromolecular complexes and how these complexes participate in the morphogenesis and functioning of the organism. Collagens are the most abundant and ubiquitous of the extracellular proteins. Mutations in several collagen genes in the nematode, C. elegans, have been shown to cause severe defects in organismal function and morphology. The powerful genetic and molecular analyses that are possible in C. elegans, and its simple anatomy, make it an excellent model system for studying the functions of collagens. Mutations in several genes that encode collagens that form the cuticle and in one gene that encodes a basement membrane collagen of C. elegans have been shown to alter the morphology and normal functioning of the organism. Different mutations in these collagen genes have different genetic properties and can cause very different morphological defects. Additional mutant alleles will be generated so that the genetic and molecular properties of further collagen defects can be examined. The effects of defined mutations will be analyzed by creating transgenic strains carrying in vitro mutagenized collagen genes. Antibodies specific for the collagens will be produced and utilized to analyze the steps of assembly of wild-type and mutant collagens into the cuticle and basement membranes. Alterations in the structure of mutant cuticles and basement membranes will be analyzed by electronmicroscopy, utilizing the specific antisera. The cuticle collagen genes have been shown to interact genetically with other genes that affect organismal morphology. These interacting genes are likely to encode proteins that interact physically, so they will also be subjected to further genetic and molecular characterization. These studies will provide insights into the genetic and molecular properties of collagens and their roles in the morphogenesis and normal functioning of the organism. The receipt of an